Research that will be conducted during the coming year will include the evaluation of infant rhesus monkeys that were born to mothers that has been exposed to PCBs (Aroclor 1248) for 18 months one year prior to their conception. Their siblings that were born while their mothers were being exposed to PCBs have shown learning and behavioral deficits for periods in excess of one year. Thus we are interested in determining how long the effects of PCB exposure on adults will be manifested in their offspring. In a second experiment, adult female rhesus monkeys are being exposed to diets containing 0.5 and 1.0 ppm PCB (Aroclor 1248) three times per week for 6 months prior to breeding. During this period, any alterations in general body health will be evaluated. Modifications in levels of serum estradiol and progesterone will be correlated with altered menstrual cycles and ability of the females to conceive. Throughout gestation the animals will be monitored for abnormalities. The infants born to females will be permitted to nurse their mothers for 4 months. During this time fat biopsies and milk samples will be obtained in order to determine PCB levels of the infants that result from intrauterine exposure and that which is an aftermath of nursing. These PCB levels will be correlated with and physical status of the infants. After 4 months, the infants will be weaned and subsequently evaluated for learning and behavioral abnormalities. In addition their physical development will continue to be monitored. The mothers of these infants will be removed from the PCB diets and their recovery rate evaluated. BIBLIOGRAPHIC REFERENCES: Allen, J.R., Carstens, L.A. and Abrahamson, L.J.: Responses of rats exposed to polychlorinated biphenyls for fifty-two weeks. Arch. Environ. Contam. Tox. 4,409-419 (1976). Barsotti, D.A., Marlar, R.J. and Allen, J.R.: Reproductive dysfunction in rhesus monkeys exposed to low levels of polychlorinated biphenyls (PCBs). Food Cosmet. Toxicol. 14, 99-103 (1976).